Impact absorbing member

ABSTRACT

An impact absorbing member includes: a first wall and a second wall that face each other; a plurality of side walls connecting these first wall and second wall; a corner portion connecting the side walls; and a destruction inducing portion, located within a predetermined area from the corner portion, for destroying the corner portion when the first wall or the second wall receives impact.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on PCT International Application No. PCT/JP2011/062206 filed on May 27, 2011, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to an impact absorbing member that absorbs impact.

2. Related Art

A general vehicle component is provided therein with an impact absorbing member. The impact absorbing member imparts cushioning properties to a vehicle. Consequently, the impact absorbing member reduces damage to a vehicle and impact added to its occupant at the time of collision. This kind of impact absorbing member is disclosed, for example, in JP-A-2002-187508.

An impact absorbing member 601 described in JP-A-2002-187508 includes, as illustrated in FIG. 18, a closed hollow portion 606 and a welded plate-shaped portion 611. The welded plate-shaped portion 611 is formed by joining and integrating the apex portions of recessed ribs 610 of a front surface wall 608 and a back surface wall 609. Furthermore, a semicircular rib-shaped portion 613 is formed on a side wall 607 of the impact absorbing member 601. The rib-shaped portion 613 is formed by recessing a part of the side wall 607 into the hollow portion 606 side. Moreover, one side surface of the rib-shaped portion 613 is open. The impact absorbing member 601 promotes improvement in impact absorbing property with these recessed rib 610 and rib-shaped portion 613. Moreover, the semicircular rib-shaped portion 613 is reduced in diameter from the opening end of the front surface wall 608 or the back surface wall 609 toward the hollow portion 606. The angle α of the reduced diameter is within a range of 5 to 30°. Moreover, the radius β of the opening end is within a range of 5 to 20 mm.

The impact absorbing member 601 is destroyed in a manner in which the side wall 607 of the impact absorbing member 601 is crushed during absorption of energy caused by impact (impact energy).

Specifically, as illustrated in FIG. 19B, when the impact absorbing member 601 is crushed, parting lines (not shown) of side walls 607 a and 607 b on both ends of the impact absorbing member 601 are bent outward. Consequently, the side walls 607 a and 607 b incline in a “<” shape. Consequently, energy by the impact is absorbed. FIG. 19A illustrates a state of the impact absorbing member 601 before being crushed. FIG. 19B illustrates a state of the impact absorbing member 601 after being crushed.

However, the side walls 607 a and 607 b, and a side wall 607 c of the impact absorbing member 601, which are illustrated in FIG. 20, may simultaneously incline in a “<” shape (buckle) by the impact as illustrated in FIG. 19B. In this case, a corner portion g connecting the side walls 607 a and 607 c is pulled in the direction a′ and the direction c′, which are illustrated in FIG. 20. As a result, the corner portion g is crushed in the impact direction as illustrated in FIG. 21. Consequently, the corner portion g is recessed inward and is folded over on itself Therefore, the corner portion g is prevented from deforming Therefore, during absorption of impact energy, the amount of compressive strain of the side walls 607 a and 607 c is different from the amount of compressive strain of the corner portion g. As a result, a load (reaction force from the impact absorbing member 601) rapidly increases from a predetermined amount of compressive strain (what is called a bottoming phenomenon occurs) at the corner portion g. In this case, a substantial maximum displaceable amount of the impact absorbing member 601 is reduced. A similar problem to that of the above-mentioned corner portion g occurs also at a corner portion h that connects the side walls 607 b and 607 c illustrated in FIG. 20.

The above-mentioned maximum displaceable amount is the maximum amount of compressive strain of the impact absorbing member 601 where an occupant or pedestrian is not injured. Moreover, the amount of compressive strain is the ratio of the thickness of the impact absorbing member 601 before deformation (represented by α in FIG. 19A) to the thickness of the impact absorbing member 601 after deformation (represented by β in FIG. 19B) (amount of compressive strain=(thickness (β) of the impact absorbing member 601 in deformation/thickness (α) of the impact absorbing member 601 before deformation)×100%).

From such points, required is an impact absorbing member that can promote the balance of the amounts of compressive strain between its side wall and corner portion during absorption of impact energy.

In a related technical document, a technology for preventing a reduction in the maximum displaceable amount is disclosed (e.g., see JP-A-2009-23521). This technology prevents deformation of a side surface from being suppressed by a wall surface being folded over on itself when an impact absorbing member is crushed.

An impact absorbing member described in JP-A-2009-23521 includes an impact absorbing rib and a depression. The depression is formed in a peripheral wall and includes symmetrical structure. The depression is composed of a substantially triangular welded surface and a pair of flat surfaces. The pair of flat surfaces connects the welded surface, and a front and a back surface wall. It prevents inhibition of deformation due to a peripheral wall's being folded over on itself when the impact absorbing member is crushed, and reduction in the maximum displaceable amount due to the inhibition.

Moreover, a technology related to stable impact absorbing performance is disclosed in JP-A-2009-161028, for example.

In the impact absorbing member of the publication, a depression is formed in a wall surface constituting the impact absorbing member. The depression defines the shapes of a corner portion or edge portion and its periphery. The depression realizes stable impact absorbing performance.

SUMMARY

An impact absorbing member includes: a first wall and a second wall that face each other; a plurality of side walls connecting these first wall and second wall; a corner portion connecting the side walls; and a destruction inducing portion, located within a predetermined area from the corner portion, for destroying the corner portion when the first wall or the second wall receives impact.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partially cutaway perspective view of an impact absorbing member according to a first embodiment;

FIG. 2 is a top view of the impact absorbing member;

FIG. 3 is a perspective view of a configuration example of a corner portion of the impact absorbing member;

FIG. 4 is a cross-sectional view taken along line A-A of FIG. 1;

FIG. 5 is a cross-sectional view taken along line B-B of FIG. 1;

FIG. 6 is a cross-sectional view illustrating an aspect of blow-molding the impact absorbing member;

FIG. 7 is a cross-sectional view illustrating an aspect of clamping the impact absorbing member;

FIG. 8 is a perspective view of another configuration example of the corner portion of the impact absorbing member;

FIG. 9 is a view illustrating increase in loads in a case where a destruction inducing portion is provided to the corner portion and in a case where the destruction inducing portion is not provided to the corner portion;

FIGS. 10A and 10B are views of the destruction inducing portion provided at the apex of the corner portion;

FIG. 11 is a view of the destruction inducing portion provided within a predetermined area from the corner portion;

FIG. 12 is a view for explaining an area around the corner portion;

FIGS. 13A and 13B are views of a preferred range of angles of the apex of the corner portion provided with the destruction inducing portion;

FIG. 14 is a view of a first configuration example of a destruction inducing portion of a second embodiment;

FIG. 15 is a view of the first configuration example of the destruction inducing portion of the second embodiment;

FIG. 16 is a view of a second configuration example of the destruction inducing portion of the second embodiment;

FIG. 17 is a view of the second configuration example of the destruction inducing portion of the second embodiment;

FIG. 18 is a view of a configuration example of an impact absorbing member related to the present disclosure;

FIG. 19A is a view of the impact absorbing member in a state before being crushed, and FIG. 19B is a view of the impact absorbing member in a state of being crushed;

FIG. 20 is a view illustrating the direction of force exerted on a corner portion of the impact absorbing member; and

FIG. 21 is a view illustrating a state where the corner portion is recessed inward and the corner portion is folded over on itself.

DETAILED DESCRIPTION

In the following detailed description, for purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

The above documents disclose the impact absorbing members for ensuring desired impact absorbing performance. However, these documents do not disclose or suggest any point to promote the balance of the amounts of compressive strain between the side wall and the corner portion during absorption of impact energy.

In the present disclosure, an impact absorbing member is provided. In the impact absorbing member, it is possible to promote the balance of the amounts of compressive strain between a side wall and a corner portion during absorption of impact energy. The amount of compressive strain is the ratio of the thickness of the impact absorbing member before deformation to the thickness of the impact absorbing member after deformation.

First Embodiment <Outline>

Firstly, an outline of an impact absorbing member 100 according to the present embodiment will be described with reference to FIGS. 1 to 3 and 8.

The impact absorbing member 100 absorbs impact energy at the time of collision. Side walls 3 of the impact absorbing member 100 are connected by corner portions 20. At least one destruction inducing portion 21 (refer to FIG. 3) or 31 (refer to FIG. 8) is provided around the corner portion 20. The destruction inducing portion 21 or 31 destroys the periphery of the corner portion 20 when the impact absorbing member 100 receives impact. Consequently, it is possible to promote the balance of the amounts of compressive strain between the side wall 3 and the corner portion 20 during absorption of impact energy. The impact absorbing member 100 will be described below in detail with reference to the accompanying drawings.

<Configuration Example of Impact Absorbing Member 100>

Firstly, a configuration example of the impact absorbing member 100 will be described with reference to FIGS. 1 to 5. FIG. 1 is a partially cutaway perspective view of the impact absorbing member 100. FIG. 2 is a top view of the impact absorbing member 100. FIG. 3 is a perspective view of a configuration example of the corner portion 20 of the impact absorbing member 100. FIG. 4 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 5 is a cross-sectional view taken along line B-B of FIG. 1.

The impact absorbing member 100 has a hollow shape. The impact absorbing member 100 is formed by blow-molding thermoplastic resin. As illustrated in these drawings, the impact absorbing member 100 includes a hollow portion 2, the side walls 3, a first wall 4, and a second wall 5.

The first wall 4 of the impact absorbing member 100 includes recessed ribs 6. The recessed rib 6 is a portion recessed into the second wall 5. The second wall 5 includes recessed ribs 7. The recessed rib 7 is a portion recessed into the first wall 4. The recessed rib 6 and the recessed rib 7 are provided so as to face each other. The bottom portions (apex portions) of the recessed ribs 6 and 7 are in contact with and welded to each other. Thus, these bottom portions form a welded surface 8. Side surfaces of the recessed ribs 6 and 7 may have a substantially tubular shape. Moreover, the side surfaces of the recessed ribs 6 and 7 may have another arbitrary shape such as a substantially triangular tube shape, a substantially quadrangular tube shape, or a substantially polygonal tube shape.

Moreover, connecting ribs 9 are formed on the first wall 4 side of the impact absorbing member 100. The connecting rib 9 connects the recessed ribs 6. Consequently, strength and stiffness of the impact absorbing member 100 against impact are increased. The connecting rib 9 may be formed on the second wall 5 side so as to connect the recessed ribs 7. Moreover, the connecting ribs 9 may be formed both on the first wall 4 side and the second wall 5 side. Moreover, the shape of the connecting rib 9 is not particularly limited. The shape of the connecting rib 9 may be, for example, shapes disclosed in FIGS. 6 to 8, and the like of JP-A-2002-187508.

Moreover, the side wall 3 of the impact absorbing member 100 connects the first wall 4 and the second wall 5. A mounting piece 10 is formed on the side wall 3. The mounting piece 10 extends from the vicinity of a parting line PL toward the second wall 5 side. An end of the mounting piece 10 is provided with a mounting hole 11. The impact absorbing member 100 is screwed on a vehicle component or the like via the mounting hole 11 of the mounting piece 10.

Moreover, a semicircular recessed rib 12 is provided to the first wall 4 of the side wall 3. Moreover, a semicircular recessed rib 12 is provided to the second wall 5 of the side wall 3. The recessed ribs 12 and 13 are formed by recessing a part of the side wall 3 into the hollow portion 2 side (inward). One side surfaces of the recessed ribs 12 and 13 are open. The semicircular recessed ribs 12 and 13 are in contact with the side wall 3 differently from the substantially tubular recessed ribs 6 and 7.

The inner diameters of the semicircular recessed ribs 12 and 13 are reduced from the opening ends of the first wall 4 and the second wall 5, respectively, toward the hollow portion 2. Therefore, in the impact absorbing member 100, the side wall 3 inclines in a “<” shape upon absorption of impact energy (when the impact absorbing member 100 is crushed).

Moreover, the bottom portions of the semicircular recessed ribs 12 and 13 are in contact with each other at substantially a middle position between the first wall 4 and the second wall 5. Thus, a plate-shaped portion 14 is formed. Consequently, a cushioning effect (reinforcement effect) of the impact absorbing member 100 is increased more.

Moreover, as illustrated in FIGS. 2 and 3, the corner portion 20 of the impact absorbing member 100 is provided with the destruction inducing portion 21. The destruction inducing portion 21 destroys the corner portion 20 (and the periphery of the corner portion 20) when the impact absorbing member 100 is crushed. The destruction inducing portion 21 includes opening ends 22 at the first wall 4 and the second wall 5. The destruction inducing portion 21 is formed by recessing parts of the first wall 4 and the second wall 5 into the hollow portion 2 side (inward). The corner portion 20 is a part that connects the side walls 3. As illustrated in FIGS. 1 and 2, in the impact absorbing member 100, its four corners correspond to the corner portions 20. Only the opening end 22 of the first wall 4 is illustrated in FIG. 2; however, the opening end 22 similar to that of the first wall 4 is formed at the second wall 5.

The destruction inducing portion 21 includes a substantially quadrangular welded surface 211 as illustrated in FIG. 3. The welded surface 211 includes a first side 211 a located on the parting line PL, a second side 211 b facing the first side 211 a, a third side 211 c and a fourth side 211 d, which connect the first side 211 a and the second side 211 b. The length (width) of the first side 211 a and the second side 211 b is within a range of 2.5 to 20 mm, preferably approximately 5 mm. Moreover, the length of the third side 211 c and the fourth side 211 d is within a range of 2.5 to 20 mm, preferably approximately 5 mm.

The destruction inducing portion 21 has a substantially quadrangular prism shape extending in the direction substantially orthogonal to the first wall 4 and the second wall 5. The destruction inducing portion 21 includes the substantially quadrangular welded surface 211, a pair of flat surfaces 212, a pair of flat surfaces 213, and a pair of flat surfaces 214. The flat surfaces 212 extend from the fourth side 211 d to the first wall 4 and the second wall 5. The flat surfaces 213 extend from the third side 211 c to the first wall 4 and the second wall 5. The flat surfaces 214 extend from the second side 211 b to the first wall 4 and the second wall 5. The pairs of the flat surfaces 212, 213, and 214 are provided so as to be substantially parallel with the impact direction. However, the pairs of the flat surfaces 212, 213, and 214 may deviate from the direction parallel with the impact direction by an angle within a predetermined range (e.g., an angle within a range of 3 to 80°).

In the destruction inducing portion 21, a ridge line 215 is formed at the position where the flat surfaces 213 and 214 intersect. Moreover, a ridge line 216 is formed at the position where the flat surfaces 212 and 214 intersect. The cross-sections of the ridge lines 215 and 216 are a circular arc with the curvature radius of 1.0 mm or less. In other words, the ridge line 215 is the portion where the flat surfaces 213 and 214 are in contact with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. On the other hand, the ridge line 216 is the portion where the flat surfaces 212 and 214 are in contact with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. The ridge lines 215 and 216 are formed so as to be substantially orthogonal to the welded surface 211.

In this manner, in the destruction inducing portion 21, the cross-sections of the ridge lines 215 and 216 are a circular arc with the curvature radius of 1.0 mm or less. Because of such a shape, the ridge lines 215 and 216 are locally thin portions. Therefore, the destruction inducing portion 21 (the ridge lines 215 and 216) is likely to rupture when receiving impact. The ridge lines 215 and 216 may deviate from a line orthogonal to the welded surface 211 by an angle within a predetermined range (e.g., 3 to 80°).

As illustrated in FIG. 3, the destruction inducing portion 21 includes a first recess 21 a and a second recess 21 b. The shape of the first recess 21 a and the second recess 21 b is a substantially quadrangular prism shape having an open side surface. The first recess 21 a is formed by recessing the corner portion 20 of the first wall 4 from the opening end 22 into the hollow portion 2 side (inward). The second recess 21 b is formed by recessing the corner portion 20 of the second wall 5 from the opening end 22 into the hollow portion 2 side. The first recess 21 a and the second recess 21 b are joined and welded to each other. Consequently, the substantially quadrangular welded surface 211 is formed.

In the destruction inducing portion 21, the ridge lines 215 and 216 being thin portions (stress-concentrated area portions) are formed in the first recess 21 a and the second recess 21 b. Therefore, if the impact absorbing member 100 (the first wall 4 or the second wall 5) receives impact, stress is concentrated on these ridge lines 215 and 216. Therefore, when the impact absorbing member 100 is crushed, rupture of the destruction inducing portion 21 and opening of a part of the corner portion 20 are possible. The thickness of the thin portions (the ridge lines 215 and 216) can be set to arbitrary thickness insofar as the thin portions are thinner than the other wall portions 3, 4, and 5 constituting the impact absorbing member 100. For example, if the average thickness of the other wall portions 3, 4, and 5 constituting the impact absorbing member 100 is approximately 2.0 mm, it is preferable that the thickness of the thin portion be 0.5 mm or less. As illustrated in FIG. 3, the destruction inducing portion 21 includes the flat surfaces 212, 213, and 214 having straight sides. The ridge lines 215 and 216 are formed at the positions where these flat surfaces 212, 213, and 214 intersect. The cross-sections of the ridge lines 215 and 216 are a circular arc with the curvature radius of 1.0 mm or less. However, the flat surfaces 212, 213, and 214 may include an arc-shaped side. The ridge lines 215 and 216 may be formed at the positions where the flat surfaces 212, 213, and 214 intersect. The cross-sections of the ridge lines 215 and 216 may be a circular arc with the curvature radius of 1.0 mm or less. In other words, the shape of the destruction inducing portion 21 may not be a quadrangular prism shape, but a substantially quadrangular prism shape.

<Method of Manufacturing Impact Absorbing Member 100>

Next, a method of manufacturing the impact absorbing member 100 will be described with reference to FIGS. 6 and 7. FIG. 6 is a cross-sectional view illustrating an aspect of blow-molding the impact absorbing member 100. FIG. 7 is a cross-sectional view illustrating an aspect of clamping the impact absorbing member 100.

The impact absorbing member 100 can be manufactured, for example, by known blow-molding and sheet blow-molding, which use thermoplastic resin. The thermoplastic resin may be resin having high mechanical strength such as stiffness. The resin includes, for example, polyolefin-based resin such as polyethylene and polypropylene, styrene-based resin such as polystyrene and ABS resin, polyester-based resin such as polyethylene terephthalate, polyamide, and a mixture thereof.

The material of the impact absorbing member 100 is resin. It is preferable that the resin be resin that facilitates formation of an opening at the corner portion 20 by rupture of the destruction inducing portion 21. Accordingly, preferred resin includes, for example, polypropylene, ABS resin, high impact polystyrene (HIPS), and polyphenylene ether resin. Furthermore, preferred resin includes a blend thereof or polymer alloy. Moreover, preferred resin has a flexural modulus of 10000 kg/cm² or more. Moreover, preferred resin has an Izod impact value at normal temperature within a range of 35 kg/cm² or less.

Polymer alloy of polyolefin-based resin and amorphous resin may be selected as thermoplastic resin as a material of the impact absorbing member 100. In this case, it becomes easier to form an opening at the corner portion 20 by rupture of the destruction inducing portion 21.

The impact absorbing member 100 is manufactured by blow-molding as illustrated in FIGS. 6 and 7. In the blow-molding, a pair of split mold blocks 19 and 19, recessed rib forming cavities 15 and 15, and an extrusion die 16 are used.

As illustrated in FIG. 6, parison 17 is disposed between the pair of split mold blocks 19 and 19. Clamping is subsequently performed as illustrated in FIG. 7. The parison 17 is subsequently pierced by a blow nozzle (not shown) to introduce pressurized air into the parison 17. Consequently, it is possible to form the impact absorbing member 100 illustrated in FIG. 1.

As illustrated in FIG. 3, the impact absorbing member 100 illustrated in FIG. 1 is provided with the destruction inducing portion 21 having a substantially quadrangular prism shape at the corner portion 20. However, the shape of the destruction inducing portion 21 is not limited to a substantially quadrangular prism shape. It is sufficient if the shape of the destruction inducing portion is a shape that ruptures when receiving impact to enable destruction of a part of the corner portion 20. The shape of the destruction inducing portion may be, for example, a substantially polygonal prism shape (such as a substantially triangular prism shape). The impact absorbing member 100 illustrated in FIG. 8 includes the destruction inducing portion 31 having a substantially triangular prism shape.

The destruction inducing portion 31 illustrated in FIG. 8 includes a substantially triangular welded surface 311. The welded surface 311 includes a first side 311 a located on the parting line PL, and a second side 311 b and a third side 311 c, which are in contact with the first side 311 a.

The destruction inducing portion 31 has a substantially triangular shape extending in the direction substantially orthogonal to the first wall 4 and the second wall 5. The destruction inducing portion 31 includes the substantially triangular welded surface 311, a pair of flat surfaces 312, and a pair of flat surfaces 313. The flat surfaces 312 extend from the second side 311 b to the first wall 4 and the second wall 5. The flat surfaces 313 extend from the third side 311 c to the first wall 4 and the second wall 5. The pairs of the flat surfaces 312 and 313 are provided so as to be substantially parallel with the impact direction. However, the pairs of the flat surfaces 312 and 313 may deviate from the direction parallel with the impact direction by an angle within a predetermined range (e.g., an angle within a range of 3 to 80°).

In the destruction inducing portion 31, it is preferable that the length of the second side 311 b and the length of the third side 311 c be almost equal. In this case, the welded surface 311 has a substantially isosceles triangular shape. The length of the first side 311 a is approximately 2.5 mm to 20 mm, preferably approximately 5 mm. Moreover, the length of the second side 311 b and the third side 311 c is approximately 2 mm to 16 mm, preferably approximately 3 mm.

In the destruction inducing portion 31, a ridge line 314 is formed at the position where the flat surfaces 312 and 313 intersect. The cross-section of the ridge line 314 is a circular arc with the curvature radius of 1.0 mm or less. In other words, the ridge line 314 is the portion where the flat surfaces 312 and 313 are in contact with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. The ridge line 314 is formed so as to be substantially orthogonal to the welded surface 311. The ridge line 314 may deviate from a line orthogonal to the welded surface 311 by an angle within a predetermined range (e.g., 3 to 80°).

In this manner, in the destruction inducing portion 31, the cross-section of the ridge line 314 is a circular arc with the curvature radius of 1.0 mm or less. Therefore, the ridge line 314 is locally a thin portion. Therefore, the destruction inducing portion 31 (the ridge line 314) is likely to rupture when receiving impact.

The destruction inducing portion 31 includes a first recess 31 a and a second recess 31 b. The shape of the first recess 31 a and the second recess 31 b is a substantially triangular prism shape having an open side surface. The first recess 31 a is formed by recessing the corner portion 20 of the first wall 4 from the opening end 22 into the hollow portion 2 side. The second recess 31 b is formed by recessing the corner portion 20 of the second wall 5 from the opening end 22 into the hollow portion 2. The first recess 31 a and the second recess 31 b are joined and welded to each other. Consequently, the substantially triangular welded surface 311 is formed.

In the destruction inducing portion 31, the ridge line 314 being a thin portion (stress-concentrated portion) is formed in the first recess 31 a and the second recess 31 b. Therefore, when the impact absorbing member 100 is crushed, rupture of the destruction inducing portion 31 and opening of a part of the corner portion 20 are possible.

In this manner, the shape of the destruction inducing portion of the impact absorbing member 100 may be any substantially polygonal prism shape insofar as it is configured to have a thin portion (stress-concentrated area portion). As illustrated in FIG. 8, the destruction inducing portion 31 includes the flat surfaces 312 and 313 having straight sides. The ridge line 314 is formed at the position where the flat surfaces 312 and 313 intersect. The cross-section of the ridge line 314 is a circular arc with the curvature radius of 1.0 mm or less. However, the flat surfaces 312 and 313 may include an arc-shaped side. The ridge line 314 may be formed at the position where the flat surfaces 312 and 313 intersect. The cross-section of the ridge line 314 may be a circular arc with the curvature radius of 1.0 mm or less. In other words, the shape of the destruction inducing portion 31 may not be a triangular prism shape, but a substantially triangular prism shape.

The destruction inducing portion 21 having a substantially quadrangular prism shape illustrated in FIG. 3 can include a thin portion (ridge line) that is thinner than the destruction inducing portion 31 having a substantially triangular prism shape illustrated in FIG. 8. Furthermore, the destruction inducing portion 21 can include more stress-concentrated area portions (ridge lines) than the destruction inducing portion 31. Therefore, the destruction inducing portion 21 is more likely to rupture than the destruction inducing portion 31 when receiving impact.

Moreover, the destruction inducing portion 21 having a substantially quadrangular prism shape illustrated in FIG. 3 includes the three flat surfaces 212, 213, and 214. On the other hand, the destruction inducing portion 31 having a substantially triangular prism shape illustrated in FIG. 8 includes the two flat surfaces 312 and 313. Therefore, the destruction inducing portion 21 has higher stiffness than the destruction inducing portion 31. Therefore, the destruction inducing portion 21 has higher impact resistance than the destruction inducing portion 31.

<Operation and Effect of Impact Absorbing Member 100>

The corner portion 20 of the impact absorbing member 100 is provided with the destruction inducing portion 21 (refer to FIG. 3) or the destruction inducing portion 31 (refer to FIG. 8). These destruction inducing portions 21 and 31 destroy the corner portion 20 when the impact absorbing member 100 (the first wall 4 or the second wall 5) receives impact. Consequently, it is possible to promote the balance of the amounts of compressive strain between the side wall 3 and the corner portion 20 during absorption of impact energy.

For example, a corner portion of a known impact absorbing member is recessed inward when receiving impact. Therefore, the corner portion is folded over on itself and is prevented from deforming Therefore, during absorption of impact energy, the amount of compressive strain of the side wall is different from the amount of compressive strain of the corner portion. As a result, a load rapidly increases from a predetermined amount of compressive strain (50% in FIG. 9) (what is called a bottoming phenomenon occurs) at the corner portion as indicated by a dotted line A in FIG. 9. “Load” is reaction force that the impact absorbing member 100 exerts when receiving impact. In this case, a substantial maximum displaceable amount of the impact absorbing member is reduced. The vertical axis of FIG. 9 represents a load (kN), and the horizontal axis represents the amount of compressive strain (%). The maximum displaceable amount is the maximum amount of compressive strain of the impact absorbing member where an occupant or pedestrian is not injured.

In contrast, the impact absorbing member 100 of the present embodiment is provided with the destruction inducing portion 21 at the corner portion 20. When the impact absorbing member 100 is crushed, the destruction inducing portion 21 destroys the corner portion 20. Therefore, the amount of compressive strain of the corner portion 20 approaches that of the side wall 3. Consequently, it is possible in the impact absorbing member 100 to promote the balance of the amounts of compressive strain between the side wall 3 and the corner portion 20 during absorption of energy caused by impact. As a result, with regard to the corner portion 20, as indicated by a solid line B of FIG. 9, if the amount of compressive strain reaches a predetermined value (50% in FIG. 9), the corner portion 20 is destroyed. Therefore, it is possible to suppress increase in a load (reaction force) from the impact absorbing member 100 until the amount of compressive strain reaches 80%. Therefore, reduction in the substantial maximum displaceable amount of the impact absorbing member 100 is suppressed.

In the above embodiment, as illustrated in FIGS. 10A and 10B, the destruction inducing portion 21 or 31 is provided to an apex portion of the corner portion 20. However, as illustrated in FIG. 11, the destruction inducing portion 21 or 31 may be provided so as to be located within a predetermined area from the corner portion 20 (e.g., within 50 mm from an end portion of a curved portion of the corner portion 20). Also in this configuration, it is possible to obtain effect similar to that of the configuration illustrated in FIGS. 10A and 10B. The curved portion of the corner portion 20 is a portion that forms a curved shape of the corner portion 20. The end portion of the curved portion is a border portion between the curve-shaped portion of the corner portion 20 and the straight line-shaped portion of the side wall 3.

As illustrated in FIG. 11, the corner portion 20 may be located between a first side wall 3 that is not provided with the semicircular recessed rib 13, and a second side wall 3′ that is provided with the semicircular recessed rib 13. In this case, it is preferable that the destruction inducing portion 21 or 31 be disposed within a predetermined area from the corner portion 20.

For example, if the destruction inducing portion 21 or 31 is not provided in the configuration illustrated in FIG. 11, when the impact absorbing member 100 receives impact, the amount of strain is larger at the first side wall 3 than on the second side wall 3′ side. Therefore, the first side wall 3 and the second side wall 3′ have different amount of strain from each other. If the destruction inducing portion 21 or 31 is provided to the second side wall 3, when the impact absorbing member 100 receives impact, the destruction inducing portion 21 ruptures due to strain of the first side wall 3, and a part of the corner portion 20 is destroyed. As a result, it is possible to bring the amount of compressive strain of the corner portion 20 close to that of the first side wall 3. As a result, even if the first side wall 3 and the second side wall 3′ have different amount of strain from each other, it is possible to promote the balance of the amounts of compressive strain between the first side wall 3 and the corner portion 20.

A predetermined area from the corner portion 20 where the destruction inducing portion 21 or 31 is provided will be described in more detail. As illustrated in FIG. 12, in a state where the amount of compressive strain of the impact absorbing member 100 has reached the maximum displaceable amount (a state where the amount of compressive strain has reached 80%), the side wall 3 of the impact absorbing member 100 includes a portion 3A that has been bent, a portion 3B that has not been bent, and border portion 3C between these. The above predetermined area may be an area from an apex 20A of the corner portion 20 to the border portion 3C.

Moreover, the destruction inducing portion 21 or 31 may be provided both to the apex 20A of the corner portion 20 and within an area from the apex 20A of the corner portion 20 to the border portion 3C. Moreover, the destruction inducing portion 21 or 31 may not be provided to the apex 20A of the corner portion 20, but a plurality of the destruction inducing portions 21 or 31 may be provided within the above predetermined area. In this manner, a plurality of the destruction inducing portions 21 or 31 may be provided within the predetermined area from the corner portion 20 (around the corner portion 20). Consequently, a crack (rupture portion) is likely to occur around the corner portion 20. Furthermore, it is possible to facilitate promotion of the balance of the amounts of compressive strain between the side wall 3 and the corner portion 20. Moreover, the destruction inducing portion 21 or 31 may be provided not only around the corner portion 20 but also to the side wall 3. Consequently, a crack is likely to occur around the corner portion 20 and at the side wall 3. It is possible to facilitate promotion of the balance of the amounts of compressive strain between the side wall 3 and the corner portion 20.

Moreover, an end portion 40 of the destruction inducing portions 21 and 31 may have a pointed shape. Moreover, the end portion 40 may have a polygonal or round shape. In this case, the end portion 40 of the destruction inducing portions 21 and 31 is provided with a surface. Consequently, when the impact absorbing member 100 receives impact, it is possible to prevent the end portion of the destruction inducing portions 21 and 31 from being damaged.

Moreover, as illustrated in FIG. 2, the destruction inducing portion 21 may be provided to the corner portions 20 on the four corners of the impact absorbing member 100. Moreover, as illustrated in FIGS. 13A and 13B, it is preferable that the destruction inducing portion 21 be provided to the corner portion 20 whose apex angle is within a range of 45° to 120°. Providing the destruction inducing portion 21 to such a corner portion 20 facilitates rupture of destruction inducing portion 21 and the destruction of a part of the corner portion 20 when the impact absorbing member 100 is crushed. As a result, it is possible to bring the amount of compressive strain of the corner portion 20 close to that of the side wall 3. As illustrated in FIGS. 13A and 13B, it is preferable that the destruction inducing portion 31 illustrated in FIG. 8 also be provided to the corner portion 20 whose apex angle is within a range of 45° to 120°.

Second Embodiment

Next, a second embodiment will be described.

The impact absorbing member 100 of the first embodiment is provided with the destruction inducing portion 21 having a substantially quadrangular prism shape illustrated in FIG. 3 or the destruction inducing portion 31 having a substantially triangular prism shape illustrated in FIG. 8, at the corner portion 20.

The corner portion 20 is a portion that can be naturally made thinner during blow-molding. Therefore, if the destruction inducing portion 21 having a substantially quadrangular prism shape illustrated in FIG. 3 or the destruction inducing portion 31 having a substantially triangular prism shape illustrated in FIG. 8 is provided to the corner portion 20, the thin portion (ridge line) of the destruction inducing portion 21 or 31 may become too thin. In this case, the stiffness of the impact absorbing member 100 against impact may become insufficient.

Therefore, as illustrated in FIG. 14, a depression 50 may be provided on at least one of the first wall 4 side or the second wall 5 side of the destruction inducing portion 21. The depression 50 has higher stiffness than the destruction inducing portion 21. In the configuration illustrated in FIG. 14, the substantially crescent depression 50 is formed on the first wall 4 side of the destruction inducing portion 21 having a substantially quadrangular prism shape. As illustrated in FIG. 15, the depression 50 may similarly be provided on at least one of the first wall 4 side or the second wall 5 side of the destruction inducing portion 31. In the configuration illustrated in FIG. 15, the substantially crescent depression 50 is formed on the first wall 4 side of the destruction inducing portion 31 having a substantially triangular prism shape.

In this manner, in the impact absorbing member 100 of the present embodiment, the substantially crescent depression 50 is formed in the destruction inducing portion 21 or 31. Consequently, even if the thin portion of the destruction inducing portion 21 or 31 provided to the corner portion 20 becomes too thin, the depression 50 can suppress reduction in stiffness (strength) against impact. In this manner, forming the substantially crescent depression 50 in the destruction inducing portion 21 or 31 can ensure the stiffness of the impact absorbing member 100 against impact.

The depression 50 has higher stiffness than the destruction inducing portions 21 and 31. Consequently, as illustrated in FIGS. 14 and 15, open width b of the depression 50 is larger than open width a of the destruction inducing portions 21 and 31 (b>a). Consequently, the stiffness of the depression 50 can be made higher than that of the destruction inducing portions 21 and 31. Moreover, as illustrated in FIGS. 14 and 15, a ridge line 51 is formed at the depression 50. The cross-section of the ridge line 51 is a circular arc with the curvature radius of 1.0 mm or more. The depression 50 is formed so that the curvature radius of the ridge line 51 is larger than 1.0 mm. Consequently, the depression 50 becomes more difficult to be destroyed than the destruction inducing portions 21 and 31.

In this manner, in the impact absorbing member 100 of the present embodiment, the substantially crescent depression 50 is formed in the destruction inducing portions 21 and 31. Consequently, the depression 50 suppresses reduction in the impact resistant strength of the impact absorbing member 100. Furthermore, also in the impact absorbing member 100 of the present embodiment, when the impact absorbing member 100 receives impact, the destruction inducing portions 21 and 31 rupture, and a part of the corner portion 20 is destroyed.

The shape of the depression 50 is not limited to a substantially crescent shape illustrated in FIGS. 14 and 15. The shape of the depression 50 may be, for example, a substantially quadrangular prism shape illustrated in FIG. 16, or a substantially triangular prism shape illustrated in FIG. 17.

In the configuration illustrated in FIG. 16, the depression 50 having a substantially quadrangular prism shape that is larger than the destruction inducing portion 21 is formed on the first wall 4 side of the destruction inducing portion 21 having a substantially quadrangular prism shape. The depression 50 includes three flat surfaces 512, 513, and 514 parallel with the impact direction. Two ridge lines 51′ are formed at the positions where the three flat surfaces 512, 513, and 514 intersect. The cross-sections of the two ridge lines 51′ are a circular arc with the curvature radius of 1.0 mm or less. In other words, one of the ridge lines 51′ is the portion where the flat surfaces 512 and 514 are in contact with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. The other ridge line 51′ is the portion where the flat surfaces 513 and 514 are in contact with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. The two ridge lines 51′ are stress-concentrated area portions (thin portions). Moreover, the depression 50 includes one flat surface 511 parallel with the welded surface 211. The width b of the flat surface 511 is larger than the width a of the welded surface 211.

In the configuration illustrated in FIG. 17, the depression 50 having a substantially triangular prism shape that is larger than the destruction inducing portion 31 is formed on the first wall 4 side of the destruction inducing portion 31 having a substantially triangular prism shape. The depression 50 includes the two flat surfaces 512 and 513 parallel with the impact direction. One ridge line 51′ is formed at the position where the two flat surfaces 512 and 513 intersect. The cross-section of the ridge line 51′ is a circular arc with the curvature radius of 1.0 mm or less. In other words, the ridge line 51′ is the portion where the flat surfaces 512 and 513 are in contact in with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. The ridge line 51′ is a stress-concentrated area portion (thin portion). Moreover, the depression 50 includes the one flat surface 511 parallel with the welded surface 311. The width b of the flat surface 511 is larger than the width a of the welded surface 311.

The depressions 50 illustrated in FIGS. 16 and 17 include the flat surfaces 512, 513, and 514 parallel with the impact direction. Therefore, the impact absorbing member 100 has high stiffness with respect to the impact direction. Moreover, the ridge line(s) 51′ is/are formed at the position(s) where the flat surfaces 512, 513, and 514 intersect. The cross-section of the ridge line 51′ is a circular arc with the curvature radius of 1.0 mm or less. In other words, the ridge line 51′ is the portion where the flat surfaces 512 and 513 are in contact with each other so as to form a circular arc with the curvature radius of 1.0 mm or less. The ridge line 51′ is a stress-concentrated area portion (thin portion). Moreover, the depression 50 has a substantially quadrangular prism shape or substantially triangular prism shape that is larger than the destruction inducing portions 21 and 31. Such a depression 50 suppresses reduction in the impact resistant strength of the impact absorbing member 100. Furthermore, when the impact absorbing member 100 receives impact, the destruction inducing portions 21 and 31 and the depression 50 rupture, and a part of the corner portion 20 is destroyed.

In the configurations illustrated in FIGS. 14 to 17, the depression 50 is formed in the first wall 4. Not limited to this, but the depression 50 may be formed in the second wall 5 or both the first wall 4 and the second wall 5. Moreover, it is preferable that the depression 50 be formed in a wall that receives impact.

Moreover, the ratio of the length of the destruction inducing portions 21 and 31 in the impact direction to the length of the depression 50 in this direction is not particularly limited. The depression 50 may not be formed so as to straddle the parting line PL. The parting line PL may be provided at the central position of the impact absorbing member 100 with respect to the impact direction. Moreover, the parting line PL is not limited to at this position, but may be formed at an arbitrary position. As described above, the destruction inducing portions 21 and 31 are formed by recessing a part of the first wall 4 and/or the second wall 5 from the opening end 22 into the hollow portion 2 side. The destruction inducing portions 21 and 31 formed by recessing a part of the first wall 4 may be welded to the second wall 5. The destruction inducing portions 21 and 31 formed by recessing a part of the second wall 5 may be welded to the first wall 4.

<Operation and Effect of Impact Absorbing Member 100>

The impact absorbing member 100 of the present embodiment includes the destruction inducing portion 21 or 31. The depression 50 is provided on at least one of the first wall 4 side or the second wall 5 side of the destruction inducing portion 21 or 31. The depression 50 has higher stiffness than the destruction inducing portions 21 and 31. Consequently, even if the thin portion of the destruction inducing portion 21 or 31 provided to the corner portion 20 becomes too thin, reduction in the impact resistant strength of the impact absorbing member 100 can be suppressed.

The destruction inducing portion 21 having a substantially quadrangular prism shape illustrated in FIG. 3 includes the thin portion (ridge line) that is thinner than the destruction inducing portion 31 having a substantially triangular prism shape illustrated in FIG. 8. Therefore, forming the depression 50 in the destruction inducing portion 21 strongly suppresses reduction in the impact resistant strength of the impact absorbing member 100.

The impact absorbing member 100 is a preferred embodiment of the present disclosure. The scope of the present disclosure is not limited to the impact absorbing member 100. The present disclosure can be carried out in modes where various alterations are made unless they depart from the gist thereof.

For example, the shape of the impact absorbing member 100 is designed in accordance with internal space of a vehicle component. Therefore, the first wall 4 and the second wall 5 do not always become flat. Furthermore, space between the first wall 4 and the second wall 5 do not always become constant. Generally, the width of the hollow portion 2 differs for each part. The amount of impact absorption of the impact absorbing member 100 depends on the (maximum) displaceable amount. Therefore, it is preferable that space between the first wall 4 and the second wall 5 be maximized insofar as the internal space of a vehicle component permits.

Moreover, in the above embodiments, as illustrated in FIGS. 3, 8, and 14 to 17, the destruction inducing portion 21 (31) formed in the first wall 4 and the destruction inducing portion 21 (31) formed in the second wall 5 are provided so as to be side by side (so as to be in contact with each other) along the impact direction. However, the destruction inducing portion 21 (31) formed in the first wall 4 and the destruction inducing portion 21 (31) formed in the second wall 5 may be provided so as to be displaced with respect to each other along the impact direction.

For example, in the configuration illustrated in FIG. 11, the corner portion 20 is located between the first side wall 3 where the semicircular recessed rib 13 is not provided and the second side wall 3′ where the semicircular recessed rib 13 is provided. In this case, when the first wall 4 side of the impact absorbing member 100 receives impact, the amount of strain of the first side wall 3 is larger than that of the second side wall 3′ side. Therefore, the first side wall 3 and the second side wall 3′ have different amount of strain from each other. Therefore, the destruction inducing portion 21 may be disposed on the second side wall 3 side on the first wall 4 side as illustrated in FIG. 11. As illustrated in FIG. 10A, the destruction inducing portion 21 may be disposed at the apex of the corner portion 20 on the second wall 5 side. In this case, when the first wall 4 of the impact absorbing member 100 receives impact, the first side wall 3 is strained. With this, the destruction inducing portion 21 destroys a part of the corner portion 20. Therefore, the amount of compressive strain of the corner portion 20 can be brought close to that of the first side wall 3. As a result, even if the first side wall 3 and the second side wall 3′ have different amount of strain, it is possible to promote the balance of the amounts of compressive strain between the first side wall 3 and the corner portion 20.

The impact absorbing member 100 can be provided inside vehicle components such as a door, a door trim, a body side panel, a roof panel, a pillar, and a bumper of an automobile and the like. Moreover, it is also possible to use the impact absorbing member 100 for equipment other than an automobile. It is also possible to use the impact absorbing member 100 for transport such as a train, a ship, and an airplane.

As described above, the impact absorbing member (100) according to an aspect of the present disclosure is the impact absorbing member (100) for absorbing impact energy at the time of collision, and is provided, around the corner portion (20) that connects the side walls (3) of the impact absorbing member (100), with at least one destruction inducing portion (21, 31) that destroys the periphery of the corner portion (20) when the impact absorbing member (100) receives impact.

According to this impact absorbing member, it is possible to promote the balance of the amounts of compressive strain between the side wall and the corner portion during absorption of impact energy.

In the first embodiment, the pairs of the flat surfaces 212, 213, and 214 can be formed with a gradient in a predetermined range of angles (e.g., a range of 3 to 80°) with respect to a parallel with the impact direction.

Moreover, in the destruction inducing portion 21 in the first embodiment, the ridge line 215 may be formed at the position where the planes of the flat surfaces 213 and 214 intersect, and the ridge line 216 may be formed at the position where the planes of the flat surfaces 212 and 214 intersect. The ridge lines 215 and 216 are linear portions each formed by bringing its flat surfaces into contact with each other at a curved surface having 1.00 mm R (R represents curvature radius) or less. The ridge lines 215 and 216 are formed so as to be perpendicular to the welded surface 211. Forming the ridge lines 215 and 216 so as to have 1.0 mm R or less produces local thin parts, and it makes it possible that the destruction inducing portion 21 of the present embodiment ruptures itself easily when receiving a predetermined load. Therefore, it is preferable that the ridge lines 215 and 216 be formed so as to have 1.0 mm R or less. The ridge lines 215 and 216 can be formed with a gradient in a predetermined range of angles (e.g., a range of 3 to 80°) with respect to a perpendicular to the welded surface 211

Moreover, the destruction inducing portion 21 of the first embodiment makes it possible to form thin portions by the first recess 21 a and the second recess 21 b, form stress-concentrated area portions by the ridge lines 215 and 216, rupture the destruction inducing portion 21 when the impact absorbing member 100 is crushed, and open a part of the corner portion 20.

Moreover, the destruction inducing portion 21 illustrated in FIG. 3 is composed of the straight line-shaped flat surfaces 212, 213, and 214, and is configured to form the ridge lines 215 and 216 with 1.00 mm R or less at the positions where the planes of the straight line-shaped flat surfaces 212, 213, and 214 intersect. However, the destruction inducing portion 21 can also be composed of the arc-shaped flat surfaces 212, 213, and 214, and configured to form the ridge lines 215 and 216 with 1.00 mm R or less at the positions where the planes of the arc-shaped flat surfaces 212, 213, and 214 intersect.

Moreover, the relative ratio of the portion where the depression 50 is formed to the portion where the depression 50 is not formed in the impact direction of the destruction inducing portions 21 and 31 is not particularly limited. Insofar as the depression 50 is not formed straddling the parting line PL, the depression 50 can be formed at arbitrary relative ratio, which is not particularly limited. The parting line PL can be formed, not limited to at the central position of the impact absorbing member 100, but at an arbitrary position. Therefore, the destruction inducing portions 21 and 31 of the present embodiment can be configured to have a substantially polygonal prism shape whose side surface is open, the side surface being recessed from the opening end 22 of the first wall 4 and/or the second wall 5 into the hollow portion 2 side and welded to the other wall surface.

The thin portion of the destruction inducing portion 21 having a substantially quadrangular prism shape illustrated in FIG. 3 becomes thinner than that of the destruction inducing portion 31 having a substantially triangular prism shape illustrated in FIG. 8. Therefore, it is possible to exhibit suppression of reduction in strength against a load more effectively if the depression 50 whose stiffness is made higher than that of the destruction inducing portion 21 is formed on at least one of the first wall 4 side or the second wall 5 side of the destruction inducing portion 21 having a substantially quadrangular prism shape as illustrated in FIGS. 14 and 16, than if the depression 50 whose stiffness is made higher than that of the destruction inducing portion 31 is formed on at least one of the first wall 4 side or the second wall 5 side of the destruction inducing portion 31 having a substantially triangular prism shape as illustrated in FIGS. 15 and 17.

Moreover, in the above embodiments, the destruction inducing portions 21 and 31 are provided vertically between the first wall 4 and the second wall 5 as illustrated in FIGS. 3, 8, and 14 to 17. However, the destruction inducing portions 21 and 31 can be configured to be provided obliquely between the first wall 4 and the second wall 5. For example, as illustrated in FIG. 11, assume that there are the first side wall 3 where the semicircular recessed rib 13 is not provided and the second side wall 3′ where the semicircular recessed rib 13 is provided between the side walls 3 on both ends connected by the corner portion 20. In this case, when the first wall 4 side of the impact absorbing member 100 receives impact, the amount of strain of the first side wall 3 is larger than that of the second side wall 3′ side, which results in difference in the amount of strain between the first side wall 3 and the second side wall 3′. Therefore, it is configured such that the destruction inducing portion 21 is located on the second side wall 3 side, as illustrated in FIG. 11, on the first wall 4 side, and the destruction inducing portion 21 is provided obliquely between the first wall 4 and the second wall 5 so that the destruction inducing portion 21 is located at the apex of the corner portion 20, as illustrated in FIG. 10A, on the second wall 5 side. Consequently, when the first wall 4 of the impact absorbing member 100 receives impact, the destruction inducing portion 21 destroys a part of the corner portion 20 due to strain of the first side wall 3, and the amount of compressive strain of the corner portion 20 can be brought close to that of the first side wall 3. As a result, even if the first side wall 3 and the second side wall 3′ have different amount of strain from each other, it is possible to promote the balance of the amounts of compressive strain between the first side wall 3 and the corner portion 20.

Moreover, the impact absorbing member of the present disclosure can be expressed as the following first to sixth impact absorbing members. The first impact absorbing member is an impact absorbing member for absorbing impact energy at the time of collision, and includes, around a corner portion connecting side walls of the impact absorbing member, at least one destruction inducing portion that destroys the periphery of the corner portion when the impact absorbing member receives impact.

The second impact absorbing member is one according to the first impact absorbing member, and includes a main body having a hollow portion, and a first wall and a second wall of the main body, which face each other. The destruction inducing portion has a substantially polygonal prism shape whose side surface is open, the side surface being recessed from an opening end of the first wall and/or the second wall into the hollow portion side and welded to the other wall surface, and destroys the periphery of the corner portion by a thin portion formed by the substantially polygonal prism shape when the impact absorbing member receives impact.

The third impact absorbing member is one according to the first or second impact absorbing member, and is an impact absorbing member in which the destruction inducing portion is formed in a substantially quadrangular prism shape.

The fourth impact absorbing member is one according to any one of the first to third impact absorbing members, and includes the destruction inducing portion also at the side wall.

The fifth impact absorbing member is one according to the first to fourth impact absorbing members, and is an impact absorbing member in which a depression whose stiffness is made higher than that of the destruction inducing portion is formed on at least one of the first wall side or the second wall side of the destruction inducing portion.

The sixth impact absorbing member is one according to the fifth impact absorbing member, and is an impact absorbing member in which the depression is formed with a surface parallel with the direction where the impact absorbing member receives impact.

The foregoing detailed description has been presented for the purposes of illustration and description. Many modifications and variations are possible in light of the above teaching. It is not intended to be exhaustive or to limit the subject matter described herein to the precise form disclosed. Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims appended hereto. 

What is claimed is:
 1. An impact absorbing member comprising: a first wall and a second wall, the walls facing each other; a plurality of side walls connecting these first wall and second wall; a corner portion connecting the side walls; and a destruction inducing portion, located within a predetermined area from the corner portion, for destroying the corner portion when the first wall or the second wall receives impact.
 2. The impact absorbing member according to claim 1, wherein the destruction inducing portion includes a thin portion, and has a substantially polygonal prism shape whose side surface is open.
 3. The impact absorbing member according to claim 2, wherein the destruction inducing portion has a substantially quadrangular prism shape.
 4. The impact absorbing member according to claim 1, wherein the destruction inducing portion is formed at the side wall within a predetermined area from the corner portion.
 5. The impact absorbing member according to claim 1, wherein at least one of the first wall side or the second wall side includes a depression having higher stiffness than the destruction inducing portion.
 6. The impact absorbing member according to claim 5, wherein the depression has a surface substantially parallel with a direction to receive impact. 